In 2019, Kaito Yashio and Akiho Senomiya are the sole members of the Robotics Club at Central Tanegashima High School in Kyushu, Japan. Akiho is an energetic positive-thinking girl who yearns to complete the ongoing project of the club: building a functional replica of Gunvarrel, the main robot of a once popular TV series. She will have the assistance of many people, but specially of her childhood friend Kaito, one of the top players of a well-known game called Kill-Ballad.